aromatic compounds Flashcards

1
Q

what are the three pieces of evidence to show benzene does not show the Kekule proposed structure

A

1 benzene is more stable than expected
2 all C-C bond lengths are the same
3 benzene doesn’t easily undergo addition reactions

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2
Q

what does benzene require to react with Br2

A

catalyst and reflux

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3
Q

why is benzene less reactive than expected

A

the 6 P electrons are delocalised over the ring which stabilises it

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4
Q

combustion of methyl benzene produces (flame not product)

A

a VERY smoky yellow flame
(high carbon to hydrogen ratio)

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5
Q

combustion of cyclohexene produces

A

a smoky yellow flame

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6
Q

reaction of methylbenzene with bromine water at room temperature

A

no reaction (requires a catalyst)

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7
Q

reaction of cyclohexene with bromine water at room temperature (observation)

A

orange solution becomes colourless

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8
Q

equation for methoxybenzene with a chloroalkane (with AlCl3 catalyst and heat)

A

C6H5OCH3 + RCA –> C6H4OCH3R + HCl

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9
Q

conditions for methoxybenzene and chloroalkane

A

heat
AlCl3 catalyst

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10
Q

observations of methoxybenzene and chloroalkane (4)

A

effervescence
damp blue litmus paper turns red
steamy fumes
white smoke with NH3

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11
Q

equation for nitration of methoxybenzene

A

C6H5OCH3 + HNO3 –> C6H4OCH3NO2 + H2O

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12
Q

what is an electrophile

A

a species which can accept a lone pair of electrons

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13
Q

which mechanism does benzene react with

A

electrophillic substitution

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14
Q

3 steps of an electrophilic substitution mechanism

A

1 formation of the electrophile
2 pair of electrons drawn from the ring to form a dative covalent bond with electrophile and reformation of the ring
3 regeneration of the catalyst

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15
Q

reagents and conditions for nitration of benzene (electrophilic substitution)

A

conc nitric acid and conc H2SO4 catalyst
heat at 55 degrees

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16
Q

what would happen if nitration of benzene reached above 60 degrees

A

further substitution of the ring (more nitro groups)

17
Q

reagents and conditions of halogenation of benzene

A

Br2 and FeBr3 catalyst
or
Cl2 and AlCl3 catalyst

heat

18
Q

reagents and conditions alkylation of benzene

A

alkyl halide (RCl)
AlCl3 catalyst (or FeBr3 for RBr)

heat

19
Q

why does benzene have a higher boiling point than ethanol

A

London forces between benzene molecules are stronger than hydrogen bonds between ethanol molecules

20
Q

what are the most suitable conditions for the nitration of phenol

A

dilute nitric acid at room temperature

21
Q

what does phenol produce with excess bromine water

A

2,4,6-tribromophenol